Field test of electroosmotic strengthening of soft sensitive clay

Abstract

A field test was undertaken to assess the effectiveness of electroosmosis in strengthening the soft sensitive (Leda) clay at the Gloucester test fill site. Specially designed copper electrodes were installed to prevent gas accumulation around the electrode and to allow pore water in the soil to flow out from the cathode without pumping. The variation of settlement, shear strength, and voltage distribution during treatment was measured, and tube samples were recovered before and after treatment for laboratory tests. The results of field vane tests at different locations within the treated area and at different times indicate that the undrained shear strength increased uniformly by approximately 50% for a period of 32 days throughout the depth of the electrodes. Concurrently, an average surface settlement of 50 mm was achieved. The total power consumption was less than 1% of the total project cost, indicating that the design of the treatment system was efficient. It is evident, therefore, that substantial increase in strength as well as general improvement in soil properties may be achieved by this improved version of electroosmosis. The elimination of pumping improved the economy of the process considerably. It is hoped that the process may receive wider application as a result of these improvements. Key words: electroosmosis, electrode, polarity reversal, Gloucester test fill, soft sensitive clay, uniformity of treatment, power consumption.

Electro-Osmotic Consolidation Studies on Peat and Clayey Silt Using Electric Vertical Drain

“…Several successful field applications of electro-osmotic stabilization are quoted in literature (e.g. Fetzer 1967;Chappell and Burton 1975;Wade 1976;Lo et al 1991).…”

“…Finally, after 2 more days of consolidation without applying current, the experiment was stopped. This sequence of testing was used to determine the test variables as polarity reversal (Lo et al 1991) had been reported to have a significant effect on electro-osmotic consolidation. However, polarity reversal did not show any effect on consolidation settlement.…”

“…Energy consumption in studies of ground improvement by electro-osmotic consolidation Duration = 120 days S u-final-av = 39.2 kPa The treatment was reported to be an economical solution Polarity reversal = 51-58 days S u-final-max = 107.9 kPa Soft clay near Ottawa, Canada(Lo et al 1991) …”

Analytical Solution for Electroosmotic Consolidation Considering Nonlinear Variation of Soil Parameters

“…By applying an external electrical field to a soil mass, the pore water can be moved from anode to cathode along with the electromigration of cations, leading to the consolidation of the treated soil mass. Numerous laboratory experiments and field tests have been conducted to investigate the development of pore-water pressure and settlement during electroosmotic consolidation, and soil properties such as water content and shear strength after the treatment were measured to evaluate the effect of this technique (Bjerrum et al 1967;Esrig and Gemeinhardt 1967;Lo et al 1991;Lefebvre and Burnotte 2002;Cherepy and Wildenschild 2003;Glendinning et al 2007;Jeyakanthan et al 2011;Wu et al 2015a;Wu et al 2016). Since Casagrande (1949) first applied electroosmotic consolidation to improve the stability of fine soils, this technique has been used often in geotechnical engineering including during slope stabilization, soft ground improvement, tailing dewatering, sludge treatment, and so on (Glendinning et al 2005;Fourie et al 2007;Zhuang and Wang 2007;Jones et al 2008;Wu et al 2015b), and various methods have been proposed to improve its efficiency, such as intermittent current, electrode reversal, moving electrode, and a combination of surcharge and vacuum preloading (Shang 1998;Micic et al 2001;Yoshida et al 1999;Wu and Hu 2012;Zhan et al 2016).…”

Electro-Osmosis Chemical Treatment of High-Salinity Soft Marine Soils: Laboratory Tests

“…Based on previous studies and engineering practices [5,7,8], adding a salt solution, i.e., ECT, could enhance the electrical conductivity of the soil [23], increase the speed of dewatering, and promote the aggregation of soil particles caused by ion exchange [24 -26]. Many researchers have been performed on the ECT.…”